The present invention relates to an improved rotary sliding closure unit and to a liquid melt container, such as a melting crucible, including such rotary sliding closure unit.
U.S. Pat. No. 3,430,644 discloses a rotary sliding closure unit designed such that a rotatable, fireproof, refractory, ring-shaped plate has a sliding surface which sets flush against two separate, stationary refractory plates, one of which contains a flow-through opening or passage which aligns with a drainspout of a liquid melt container, and the other of which is located diametrically opposite the first. With this arrangement, the greatest part of the sliding surface of the rotary ring-shaped plate is constantly exposed. This inherently results in that this ring-shaped plate is insufficiently supported against the effects of exterior forces, particularly the drive system for achieving rotation of such plate. Additionally, it is difficult to align precisely the two stationary refractory plates in the base area of the sliding closure unit on a joint bearing surface for the ring-shaped rotary plate. Even further, the plates can be installed and removed only if the base plate, which is mounted directly to the outside of the liquid melt container, also is removed.